St. Mary's Church, known in German as the Marienkirche, is a church in Berlin, Germany. It is located on Karl-Liebknecht-Straße (formerly Kaiser-Wilhelm-Straße) in central Berlin, near Alexanderplatz. The exact age of the original church site and structure is not precisely known, but it was first mentioned in German chronicles in 1292. It is presumed to date from earlier in the 13th century. The architecture of the building is now largely composed of comparatively modern restoration work which took place in the late 19th century and in the post-war period. The church was originally a Roman Catholic church, but has been a LutheranProtestant church since the Protestant Reformation and a united Protestant church since the Prussian Union of churches in 1817.

Along with the Nikolaikirche, the Marienkirche is the oldest church in Berlin. The oldest parts of the church are made from granite, but most of it is built of brick, giving it its characteristic bright red appearance. This was deliberately copied in the construction of the nearby Berlin City Hall, the Rotes Rathaus. During World War II, it was heavily damaged by Allied bombs. After the war the church was in East Berlin, and in the 1950s it was restored by the East German authorities.

Before World War II, the Marienkirche was in the middle of a densely populated part of the district of Mitte, and was in regular use as a parish church. After the war, this area was cleared of ruined buildings and today the church stands in the open spaces around the Alexanderplatz, and is overshadowed by the East Berlin television tower, the Fernsehturm.

There is a striking statue of Martin Luther outside the church. The Marienkirche also contains the tomb of Field Marshal Otto Christoph von Sparr. Carl Hildebrand Freiherr von Canstein, the founder of the oldest Bible society of the world, the Cansteinsche Bibelanstalt, was buried here in 1719.